Abrasive tools and methods of making same

ABSTRACT

Abrasive tools of the disposable type applicable to many types of equipment to sand materials of various types are provided. In particular, the invention relates to devices using rotating abrasive discs for sanding machines, which include a plurality of flexible abrasive discs open at a radial cut and arranged in an overlapping and staggered configuration such as to define an abrasive, lamellar-like work surface with overlapping flaps, wherein each flap is formed of a protruding portion of an abrasive disc. Methods of making such abrasive tools are also provided.

The present invention relates to an abrasive tool of the disposable type applicable to equipment, both professional, industrial and for hobbies, to sand materials of various types having rough surfaces. In particular, the invention relates to a device using rotating abrasive discs.

The sanding of rough or in any case uneven surfaces is a procedure widely applied throughout various sectors, both crafts and industrial, such as construction, carpentry, and the processing of hard materials. Depending on the extension of the surface to be sanded, manual or portable roller sanders are used. The latter are normally used to sand floors, while the former are used to sand small surfaces and often for private use (hobbies). Vice versa, large bench sanders are used to sand untreated manufactured goods for example made from stone, resin or lacquered.

The abrasive surfaces used for sanding are of different types, both natural and synthetic. For example diamond, corundum, silica, quartz, pumice, sandstone or various synthetic oxides such as aluminium, chrome, iron, glass oxides and so forth are used. In all cases the chosen material is ground so as to obtain a predefined grain size which also depends on the type of sanding desired, it is then combined with a binding agent to make it adhere to a backing or modelled, with or without the binding agent, to form the tool, to mention just some of the more conventional methods.

The sanding of an untreated surface is usually conducted in a series of stages. Levelling and roughing are usually the first steps, followed by finishing and polishing after filling in any cracks or pores. For each of these steps an abrasive surface having a different grain is used, that is to say in which abrasive powder material has a specific grain size: the biggest grain is used to roughly sand the surface, in that it permits removal of the excess material more easily but is unable to provide a surface finish; the finer grain instead makes it possible to achieve a good finish as far as sanding the surface but cannot be used for the first rough sanding step. For certain types of material, in particular stone materials, there may be as many as ten subsequent steps starting from an abrasive surface with a coarser grain and gradually moving to a finer grain.

One type of abrasive tool used in particular for manual sanders is that of the so-called abrasive flap or lamellar discs. An abrasive disc of this type, shown by way of example in FIG. 1, is composed of a disc-shaped backing in essentially rigid material such as plastic or aluminium, onto which a plurality of abrasive fins of the desired grain are glued. The fins are arranged so as to partially overlap each other like roof tiles, which allows them to expose a sharp edge contributing greatly to the sanding action, this being the point in which the greater pressure is exerted by the operator during use. Lamellar flap discs have various advantages compared to traditional abrasive discs composed of a single disc of abrasive material, such as longer duration and high quality performance, but have the drawback of being expensive, having a rigid structure and entailing an excessive waste of material at the moment of their disposal, especially of the rigid support to which the lamellar flaps are glued.

The purpose of the present invention is therefore to make available an abrasive tool for sanding machines which resolves the drawbacks of the prior art and in particular which is flexible, lasting, of limited cost and which permits high quality performance.

Such problem is resolved by an abrasive tool as delineated in the appended claims, the definitions of which form an integral part of this description.

One object of the invention is therefore a flexible abrasive tool of the lamellar-like type re-adaptable according to the wear of the abrasive surface.

Another object of the invention is a constructionally simple abrasive tool of the lamellar-like type of a contained cost.

One further object of the invention is therefore a flexible abrasive tool of the lamellar-like type having a variable grain abrasive work surface.

Further characteristics and advantages of the present invention will be more clearly comprehensible from the description given below of as preferred and non-limiting embodiment with reference to the appended drawings, wherein:

FIG. 1 is a plan view of an abrasive lamellar flap disc according to the prior art;

FIG. 2 is a perspective transparent view of an abrasive tool according to the invention;

FIG. 3 is a plan view of an abrasive disc of the tool according to the invention;

FIG. 4 is a plan view of the abrasive disc in FIG. 3 according to a different embodiment of the invention;

FIG. 5 is an exploded side view of the abrasive tool of the invention fitted onto a manual sander;

FIGS. 6A and 6B show the sequence of operations needed to predispose the abrasive tool according to the invention;

FIG. 7 is a perspective transparent view of an abrasive tool according to a different embodiment of the invention.

With reference to the figures, the abrasive tool which the invention relates to, globally denoted by reference numeral 1, comprises a plurality of flexible abrasive discs 2, open at a radial cut 3 and arranged in an overlapping and staggered configuration such as to define an abrasive, lamellar-like work surface 4 with overlapping flaps, wherein each flap 5 is formed of a protruding portion of an abrasive disc 2.

The term “abrasive disc” is understood to mean both a correctly named disc of a circular shape and any other disc, even of a polygonal shape, suitable for use in sanding machines with rotating elements.

The term “lamellar-like” means a configuration in which a plurality of flaps 5 are positioned so as to create a partially overlapping lamellar structure, typical of the abrasive lamellar discs shown by way of example in FIG. 1.

As shown in FIG. 3, each abrasive disc 2 of the plurality of discs comprises a central hole 7 from which a plurality of slots arranged in a spoke pattern depart, so as to form flaps 9 positioned around the hole 7.

The abrasive disc 2 further comprises said radial cut 3 which extends from the peripheral rim 6 of the disc to the central hole 7.

The abrasive disc 2 is flexible. An abrasive disc suitable for the purposes of the present invention is any one of the conventional flexible abrasive discs.

The flexible abrasive discs are characterised by a backing to which a suitable abrasive powder adheres by means of a binding agent.

For example, a disc having a paper backing, typically weighing from 70 to 300 g/m² or a canvas or canvas/paper backing may be used. Alternatively the backing may be made from semi-rigid plastic material or even a thin and flexible sheet of metal, such as aluminium. In certain embodiments, the backing comprises the male or female element of a velcro fastening system on the opposite side to the abrasive side, so as to permit its removable attachment to the polishing pad of a sander which will in turn comprise the complementary velcro element.

The abrasive powder may be selected from among those commonly used in the sector depending on the type of surface to be sanded and the desired finish. For example a natural abrasive powder of diamond, corundum, quartz silica, pumice, sandstone, emery, garnet or a synthetic powder of aluminium, chrome, iron, zirconium oxides, boron nitride, silicon carbide, glass, boron carbide, ceramic-coated aluminium oxide may be used. The grain may be chosen from among those commonly used for the varying degrees of finish required, for example for artificial corundum and for silicon carbide this may be between 8 and 240 degrees, as defined in the UNI table 3898. A small number corresponds to a coarse grain, suitable for rough sanding, while the higher numbers identify an increasingly finer grain.

The binding agent may be chosen from among those widely used in the sector, such as natural glues, ureic resins and phenolic resins.

The abrasive powder on the backing may have a closed coating, that is to say with a high density of abrasive granules, suitable for hard materials and for a high quality finish; or an open coating namely with a low density of abrasive granules, suitable for ensuring high resistance to clogging. In addition, the abrasive disc may comprise additives, such as anti-clogging additives (zinc stearate) or anti-static products.

In certain embodiments, as shown in FIG. 4, the abrasive disc 102 comprises a plurality of through holes 10 on its surface, the function of which is to assist the removal of the dust formed during sanding.

FIGS. 6A and 6B show the sequence in which the abrasive tool 1 is assembled starting from a plurality of abrasive discs 2, 102. First of all, the discs are stacked, aligning the respective radial cuts 3. The discs are then bent together so as to bring the rims 11, destined to form the working rims of the tool, into a position offset from the opposite rims 12, which instead remain hidden under the abrasive surface 4 (FIG. 6A). At this point, the bottom disc of the stack is rotated in the direction of the arrow, around an axis perpendicular to the disc and passing through the centre, then in succession all the other discs from the bottom to the top, so as to achieve a staggered configuration which gives rise to the lamellar-like abrasive work surface 4 (FIG. 6 b).

The number of abrasive discs 2 composing the abrasive tool 1 may vary from a minimum of two discs to a dozen or more. By increasing the number of discs, the flap 5, that is the portion of disc emerging and thus exposed to globally form the abrasive work surface 4, becomes increasingly smaller. In addition, as the number of disks increases, the lamellar-like configuration of the tool will comprise a large number of flaps 5, each of which presenting a sharp edge 11 which constitutes the part of greatest friction and which during use works harder and is therefore subject to greatest wear.

The abrasive tool 1 may then be mounted on a polishing pad 13 of a sander 14 (shown schematically in FIG. 5) by means of a suitable stop screw 15. The pad 13 typically has a central depressed area 16 with a hole. The stop screw 15 passes through the central hole 7 of the abrasive tool and through the hole of the pad 13 before screwing onto the rotating plate 17 of the sander 14. This way, the head of the stop screw 15 is positioned under the abrasive surface 4 which is instead supported by the outer portion of the pad 13, and does not therefore interfere with the surface to be sanded. This type of attachment of the tool to the sander is permitted by the flexibility of the material with which the abrasive tool 2 is made and by the presence of the slots 8 which form the tongues 9 suitable to be bent downward and clamped between the head of the stop screw 15 and the surface of the central depressed area 16 of the polishing pad 13.

Other methods of attachment of the abrasive tool according to the invention to the sander may however also be provided for. For example the velcro system described above makes it possible to rapidly and effectively attach the abrasive tool to a pad 13.

When the abrasive surface 4, and in particular the rims 11 of the discs 2, 102 are worn, it is possible to remove, for example by cutting with scissors or another cutting tool, the worn flaps 5 or just the portion thereof comprising the edge 11, and if necessary repeating the operation of rotating the single discs shown in FIG. 6B, maintaining the initial staggering. This way, new portions of disc which will form the new flaps 5 are uncovered. It is thus possible to exploit to the most the abrasive surface of each disc 2, 102, gradually renewing the abrasive work surface 4. The single discs 2, 102 may also have radial weakening lines or in any case radial lines traced on them to facilitate the removal of the worn segment and keep a straight edge 11.

In some embodiments the discs 2, 102 which form the abrasive tool 1 have the same grain.

In other embodiments, abrasive discs of a different grain 2, 102 are used, in particular arranging the different discs in succession with an increasing (or decreasing) grain. This way it is possible to obtain the sanding and finishing of a surface in drastically shorter times than with the conventional technology which provides for subsequent passages with disks of an increasingly finer grain.

In yet other embodiments, the abrasive discs 2, 102, the same or different from each other, have a so-called multi-abrasive surface, as disclosed in the prior Italian patent application no. MI2011A000850 (filed on 16 May 2011) by the same applicant. “Multi-abrasive surface” means an abrasive surface which has separate portions having a different grain. The arrangement of such portions on the surface of the disc may be according to various criteria but in particular those of creating a path in which the grain gradually increases or decreases. Arrangements in spots, concentric circles or spirals are for example possible. Reference is in any case made to the aforementioned patent application for a clearer understanding of the structure of such discs utilisable for the purposes of the present invention.

In a different embodiment, shown in FIG. 7, the abrasive tool 201 comprises a plurality of half-moon abrasive elements 202 in place of the abrasive discs 2, 102. Such half-moon element 202 may be made from the abrasive discs 2, 102 by cutting along the entire diameter of the disc.

Each half-moon element 202 comprises an abrasive surface 204 and an opposite velcro surface 240, of the female or male type, such surface 240 being destined to cling to a velcro surface of the complementary type attached to the polishing pad 13 of a sander 14. The plurality of half-moon abrasive elements 202 are arranged so that the single elements are staggered as shown in FIG. 7 (only three abrasive elements 202 have been shown for sake of clarity), revealing the flaps 205, and the assembly thus composed is applied to the velcro on the polishing pad 13.

This embodiment has the advantage of making the fitting of the tool more practical in that the underside, that is to say the velcro surface, would make the reciprocal sliding of the whole discs difficult.

The abrasive tool 1 according to the present invention has many advantages.

First of all the abrasive tool according to the invention makes it possible to create a lamellar-like configuration by means of a simple and economical process. It is not in fact necessary to predispose the rigid backing in plastic or metal to which the flaps of conventional lamellar discs are glued. This translates not only into reduced production costs, but also into a reduced quantity of waste material at the end of the tool's life.

Moreover, the tool according to the invention combines the flexibility of conventional flexible discs with the typical characteristics of a lamellar configuration, something which is instead absent in the flap discs of the prior art.

The possibility of reciprocally rotating the various abrasive discs composing the tool makes it possible to remove the worn abrasive surface, increasing the life of the tool and making it possible to practically use almost the entire surface of each disc.

The abrasive discs composing the tool may have a different grain from one another or have a variable grain surface, as said above, which reduces the number of sanding cycles when operations are in progress.

It is evident that only one particular embodiment of the present invention has been described, so that a person skilled in the art may make all the changes needed to adapt it to specific conditions. The abrasive tool 1 according to the invention may be fitted onto various types of sanders, such as rotary sanders, orbital sanders, roto-orbital, planetary, if necessary after suitable adjustments either structural or dimensional of the various types of machine used, adaptations which fall within the normal skills of a person skilled in the art and which do not depart from the object of the present invention as defined in the appended claims. 

1-14. (canceled)
 15. An abrasive tool for sanding machines, comprising a plurality of flexible abrasive discs open at a radial cut and arranged in an overlapping and staggered configuration such as to define an abrasive, lamellar-like work surface with overlapping flaps, wherein each flap comprises a protruding portion of an abrasive disc.
 16. The abrasive tool of claim 15, wherein each abrasive disc comprises a central hole from which a plurality of slots extend in a spoke pattern, so as to form tongues positioned around the hole.
 17. The abrasive tool of claim 15, wherein said radial cut extends between the peripheral rim of a disc and its central hole.
 18. The abrasive tool of claim 15, wherein said flexible abrasive discs comprise a backing having a binding agent to which a suitable abrasive powder adheres.
 19. The abrasive tool of claim 18, wherein said backing comprises paper, preferably weighing 70 to 300 g/m², or canvas or canvas/paper; or said backing is made from semi-rigid plastic material or a thin and flexible sheet of metal, such as aluminium.
 20. The abrasive tool of claim 18, wherein said backing comprises the male or female element of a velcro fastening system on the opposite side to the abrasive side, so as to permit its removable attachment to the polishing pad of a sander comprising the complementary velcro element.
 21. The abrasive tool of claim 20, wherein said abrasive discs are replaced by half-moon abrasive elements, each abrasive half-moon element comprising an abrasive surface and an opposite velcro surface, of the female or male type, such velcro surface being destined to cling to a velcro surface of the complementary type attached to the polishing pad of a sander.
 22. The abrasive tool of claim 18, wherein said abrasive powder is selected from the group consisting of: diamond, corundum, quartz, silica, pumice, sandstone, emery, garnet and any combination thereof; or a synthetic powder selected from the group consisting of: aluminium, chrome, iron, zirconium oxides, boron nitride, silicon carbide, glass, boron carbide, ceramic-coated aluminium oxide and any combination thereof.
 23. The abrasive tool of claim 18, wherein said binding agent is selected from the group consisting of: natural glues, ureic resins and phenolic resins.
 24. The abrasive tool of claim 15, wherein said abrasive disc or said half-moon abrasive element comprises a plurality of through holes on its surface.
 25. The abrasive tool of claim 15, wherein the abrasive discs or abrasive half-moon elements have a different grain, preferably increasing or decreasing in succession.
 26. The abrasive tool of claim 15, wherein the abrasive discs the same or different from each other, have an abrasive surface which has separate portions of a different grain.
 27. A Method of making an abrasive tool comprising the following steps: providing a plurality of flexible abrasive discs having a central hole and a radial cut which extends from the peripheral rim of a disc and its central hole, said radial cut having a first and a second rim; stacking said abrasive discs, aligning the respective radial cuts; bending said abrasive discs together so as to bring the first rims, destined to form the working rims of the tool, into an offset position from the opposite second rims; rotating the lowest disc in the stack around an axis perpendicular to the disc and passing through the centre, then in succession rotating all the other discs from the bottom to the top, so as to achieve a staggered configuration which gives rise to the lamellar-like abrasive work surface.
 28. A method of renewing the worn abrasive work surface of an abrasive tool, comprising the following steps: removing the worn flaps or just the portion thereof comprising the edge; and if necessary, rotating the lowest disc in the stack around an axis perpendicular to the disc and passing through the centre, then in succession rotating all the other discs from the bottom to the top, so as to achieve a staggered configuration. 